In order to provide a commercially viable fuel system, especially for compression ignition engines, fuel injector manufacturers must satisfy an often contradictory set of performance demands, manufacturability requirements and robustness issues. Among the different performance demands are the need of the fuel injector to have the ability to inject a broad range of fuel volumes, with this problem being compounded by the need to often inject the minimal quantity close in time to another larger injection event. Among the manufacturability requirements is the need to minimize part count, devise a realistic assembly strategy and provide geometrical tolerances that result in mass produced fuel injectors that respond similarly to identical control signals. On top of these requirements are a need for the fuel injector to exhibit a durable lifespan while retaining predictable responses to control signals over its working life in the face of wear and tear in the hostile environment of an internal combustion engine.
One specific type of fuel injector that has seen considerable success, especially in relation to compression ignition engines, utilizes a so called common rail to supply pressurized fuel to individual fuel injectors mounted for direct injection in individual engine cylinders. In order to reduce undesirable emissions, such as soot and/or NOx, the fuel injector must often need to be precisely controlled to produce a sequence of fuel injection events of differing fuel volumes in precise timings. In many common rail fuel injectors, the nozzle outlets are opened and closed by a needle valve member that has a closing hydraulic surface exposed to fluid pressure in a needle control chamber, whose pressure is controlled by an electronically controlled valve. Short dwell times between injection events require that the moving components within the fuel injector settle out and reset prior to initiating a subsequent injection event in the often short dwell time between desired injection events. In addition, undesirable secondary injection events due to a valve bouncing off a valve seat can sometimes be a problematic issue. In this regard, U.S. Pat. No. 7,156,368 teaches a flow control valve that allows the armature of the electrical actuator to overtravel, and thus decouple from, the valve member after the valve member contacts its seat in order to reduce momentum, and supposedly avoid bouncing, when the valve member impacts its seat to end an injection event. While the '368 patent teaches a flow control valve structure and overtravel feature that may limit valve bounce, it may do so at the expense of other manufacturability, performance and robustness degradations.
The present disclosure is directed toward one or more of the problems set forth above.